[VIDEO] 'Living fossil' Genome: Brachiopod Rapidly Evolves, While Looking the Same

A mollusk-like creature called the lingulid brachiopod, or Lingula anatina, is thought to be a "living fossil," but researchers recently found that its genome is still actively evolving. According to a group of researchers, this study provides another stepping-stone for further understanding of animal evolution.

Brachiopods such as L. anatina are marine invertebrates that first evolved in prehistoric oceans during the early Cambrian period, approximately 520 million years ago. They quickly dominated the seas during the Paleozoic era, which was between 542 and 251 million years ago. Today, they are often confused with mollusks.

According to a news release, researchers from the Okinawa Institute of Science and Technology Graduate University (OIST), Nagoya University, and the University of Tokyo decoded over 34,000 genes of a L. anatina collected from Amami Island in Japan.

Lingulid brachiopods have maintained the same appearance since the Silurian period, roughly 443 to 419 million years ago. However, their "living fossil" nickname incorrectly implies that this species is no longer evolving, the release noted. While it is still unclear exactly how brachiopods evolved in relation to other species, the researchers concluded that they are close relatives to mollusks, but only superficially.

"At the molecular level, brachiopods are very similar to mollusks. Both are protostomes -- their embryos form mouths first and anuses thereafter. However, brachiopod embryonic development is very different from that of mollusks: it resembles that of deuterostomes, in which embryos form anuses first and mouths second," Yi-Jyun Luo, first author of the study, said in the release. "The results of the Lingula genome project will help future research of these differences and the roles that specific genes play in development of various brachiopod body structures."

While it's the Lingula's similar appearance to that of its ancient ancestors does suggest it could be a "living fossil," its genome indicates otherwise: It has actually been rapidly evolving.

The researchers observed chemical structure diversity in living Lingula shells. According to the release, when soft tissues were examined, they indicated evolutionary changes. However, the species' genes painted the clearest picture of all. The researchers concluded that Lingula lacks the genes for bone formation. So, even though there are similarities seen between Lingula and bony vertebrates, they did evolve separately from one another and form their hard tissues differently. The researchers described this as parallel evolution.

This study, recently published in Nature Communications, provides more information on the evolutionary history of brachiopods.

"This is one step toward untangling the mysteries of animal evolution. The study highlights the fact that various animals have taken evolutionary paths independently from one another." Noriyuki Satoh, professor and head of the OIST Marine Genomics Unit, said in a statement. "Conserving the natural habitat for animal diversity is important. This research illustrates the well-nurtured tradition of zoological studies in Japan."

A video detailing the recent study can be found online.

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